The present invention relates to a micro-floppy disk being smaller than an ordinary floppy disk. More particularly, it relates to a disk cartridge using a hard casing instead of a thin jacket.
A floppy disk has been widely used as an exchangeable information storage medium which is removable for storage and transportation. A small-sized floppy disk which is smaller than an ordinary floppy disk is widely used for personal computers from the economical viewpoint. The floppy disk has a thin flexible jacket which is used as a casing to protect a magnetic disk. In consideration that the thin flexible jacket type floppy disk is insufficient to protect the magnetic disk, there has been proposed a disk cartridge in which a thick, hardly deformable, strong hard casing is used and lining sheets are attached to the inner surfaces of the hard casing to receive a magnetic disk in a rotatable manner.
FIG. 2 is a perspective view showing the outline of the conventional disk cartridge; FIG. 3 is a plan view showing the inner surface of a lower hard casing 12 of the disk cartridge and FIG. 4 is a plan view showing the inner surface of an upper hard casing 10 of the cartridge.
In the Figures, reference numerals 16, 18 respectively designate openings for receiving a writing-in and reading-out head, which are opened in the upper and lower hard casings 10, 12. The openings 16, 18 are closed by a cover 14 unless the openings are used for recording and reproducing. Reference numerals 20a.sub.1, 20a.sub.2 are respectively designate curved walls provided in the inner surface of the upper hard casing 10 to define a rotating region for a magnetic disk and numerals 22a.sub.1, 22a.sub.2 respectively designate curved walls provided in the lower hard casing 12 to define the rotating region for the magnetic disk. The curved walls 20a.sub.1, 20a.sub.2 and the curved wall 22a.sub.1, 22a.sub.2 are arranged in a symmetrical position in the upper and lower hard casings 10, 12. Therefore, when the casings are assembled, the curved walls 20a.sub.1, 22a.sub.1 and the curved walls 20a.sub.2, 22a.sub.2 are respectively matched with each other. A reference numeral 24 designates an elastic piece (a lifter) whose one end 26 is bonded in the rotating region of the lower casings 12 so that the major portion of the elastic piece 24 rises in a slanting state with respect to the rotating direction of the magnetic disk. A reference numeral 28 designates a projecting member for opposing the elastic piece, which is placed in the inner surface of the upper casing 10 at a substantially symmetrical position with respect to the elastic piece 24 in the lower casing 12. The projecting member 28 comprises a plurality of projections which are equidistant and parallel to the direction of rotation of the magnetic disk. A reference numeral 30 designates an opening for a driving hub of the magnetic disk, which is formed in the center of the lower casing 12 and a numeral 32 designates a bearing part provided at the center of the inner surface of the upper casing 10.
FIG. 5 is a cross-sectional view of the conventional disk cartridge which is fitted to a driving unit. A magnetic disk 34 is held in the assembled upper and lower casings 10, 12 in a rotatable manner. The magnetic disk has a driving hub 36 to which a driving shaft 38 of the driving unit (not shown) is fitted. A lower lining sheet 42 is bonded to the lower hard casing 12 at its outer peripheral portion except for a region where the elastic piece 24 is provided in the lower hard casing 12. An upper lining sheet 40 is also bonded to the upper hard casing 10 at its outer peripheral portion except for a region where the projecting member 28 is provided opposing to the elastic piece 24 in the upper hard casing 10. The upper and lower lining sheets 40, 42 cover the magnetic disk 34 to protect it and remove dust and foreign substances from the surfaces of the magnetic disk 34. The lower lining sheet 42 is pushed up by an elastic force of the elastic piece 24 at and near the position where the elastic piece 24 is provided. The upper lining sheet 40 is pushed down by the projecting member 24. Accordingly, the upper and lower lining sheets are brought into close-contact with the magnetic disk 34 so as to increase dust removing function. Reference numerals 44, 46 designate supporters for supporting the disk cartridge on the driving unit.
In the conventional disk cartridge, however, the upper and lower lining sheets 40, 42 are not always in close-contact with the magnetic disk 34 at or near the elastic piece 24 and the projecting member 28 even though the lining sheets cover the both surfaces of the magnetic disk. When the disk cartridge is operated on the driving unit, a bearing part 32 at the center of the upper casing 10 is pushed up by the top end of the driving shaft 38, whereby the distance between the inner surfaces near the central portion of the upper and lower casings 10, 12 is widened.
FIGS. 6 and 7 are enlarged cross-sectional views of the elastic piece 24 and the projecting member 28 of the disk cartridge in which FIG. 6 is a cross-sectional view taken along a line perpendicular to the direction of rotation and FIG. 7 is a cross-sectional view taken along a line along the direction of rotation.
In FIGS. 6 and 7, each projection of the projecting member 28 for supporting the elastic piece projects from the inner surface of the upper casing 10 at the same length. Accordingly, although the projections near the outer peripheral portion make the upper lining sheet 40 in close contact with the magnetic disk 34, there arises an air gap between the upper lining sheet 40 and the magnetic disk 34 in the vicinity of the central portion of the disk cartridge, with the result that the contact between them becomes weak. Accordingly, there is a problem that dust removing function on the upper surface of the magnetic disk 34 is poor at the position near the central portion of the magnetic disk even though the lower lining sheet 42 is in uniformly contact with the mangetic disk 34 from the inner diametrical portion to the peripheral portion by means of the elastic piece 24 provided in the lower casing 12.